<!DOCTYPE html>
<html>
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <meta name="author" content="lijinbo" />
    <title>114-模拟视频没有信号</title>
    <style>
      section {
        position: absolute;
        top: -50px;
        left: -50px;
        width: calc(100% + 50px);
        height: calc(100% + 50px);
        background: repeating-linear-gradient(#111, #111 50%, #fff 50%, #fff);
        background-size: 5px 5px;
        filter: url(#noise);
      }

      svg {
        width: 0;
        height: 0;
      }
    </style>
  </head>

  <body>
    <section></section>
    <svg>
      <filter id="noise">
        <feTurbulence id="turbulence">
          <animate
            attributeName="baseFrequency"
            dur="50s"
            values="0.9 0.9;0.8 0.8;0.9 0.9;"
            repeatCount="indefinite"
          ></animate>
        </feTurbulence>
        <feDisplacementMap in="SourceGraphic" scale="60"></feDisplacementMap>
      </filter>
    </svg>
  </body>
</html>
